This invention relates to pumps, and more particularly to a pump having an anti-siphoning capability when the pump is turned off.
Pumps for transferring fluids, such as liquids, from one location to another are well known. The operation of most known pumps is usually based on the development of a suction condition in the pump to draw liquid therein and a sequential pressure condition to expel the liquid from the pump. During normal pumping operations the suction and pressure conditions often produce a siphoning effect which aids the pumping action.
However when a pump is turned off, after a siphoning condition has developed, fluid transfer through the pump may undesirably continue by virtue of the siphoning condition rather than any pumping action. This continuous siphoning after pump shutdown is generally undesirable.
On numerous occasions the fluid that is subject to a pumping operation is expensive and is usually wasted if continuous siphoning of such fluid through the pump occurs after the pump is shut down, a condition hereinafter referred to as continuous siphoning. In addition, certain fluids operated on by a pump are noxious, toxic or otherwise dangerous, and if permitted to run off due to continuous siphoning can cause undesirable contamination or pollution, in addition to an expensive cleanup problem.
In certain instances fluids that are continuously siphoned through a pump after a pump is shut down are provided with special entrapment or catch containers that occasionally overflow. Thus, the problem of uncontrolled fluid runoff due to continuous siphoning is not easily solved when transferred from one state of a pumping operation to another.
Fluid runoff from pumps, due to continuous siphoning, has long been a problem with small acreage farmers who may be financially dependent upon inexpensive pumps that are subject to continuous siphoning. The farmer often uses a pump for seed treatment wherein chemicals are added to the seed as the seed is planted. In large scale farming operations and in seed treatment plants, highly specialized equipment is capable of processing numerous tons of seed with substantial amounts of chemicals on a daily basis.
High volume systems for seed treatment generally include sophisticated and intricate control systems with an array of valves that precisely control chemical additives. Such systems are usually beyond the financial reach of the small acreage farmer.
One method of dealing with the problem of continuous pump siphoning, is disclosed in U.S. Pat. No. 2,918,878. The disclosed pump includes a bleeder valve that permits air to enter the pump to prevent continuous siphoning of fluid when the pump is shut down. However the bleeder valve must be manually positioned at the end of a pumping operation. In addition, the bleeder valve must be manually adjusted to a closed position when continuous siphoning stops or the pump will not function at its optimum level when restarted. The need for manual adjustment of the bleeder valve is a problem because the pump operation must be monitored and thus labor costs are added to the operation of the pump.
U.S. Pat. No. 1,419,273 discloses a pump with a float controlled air vent for purposes of preventing continuous siphoning. This arrangement does not provide precise shutoff control since the float must recede to a predetermined level before the air vent opens. Under the disclosed air vent arrangement, it is possible for significant amounts of liquid to flow through an outlet faucet after the pump is shut down and before the air vent opens.
In addition to continuous siphoning, another problem associated with pumps of the type described is the possibility of damage to the pump when the pump discharge is blocked or otherwise obstructed. If a pump continues to operate while an obstruction prevents discharge of fluid, the pump may stall and become damaged.
It is thus desirable to provide a pump with an anti-siphoning capability that operates automatically to provide a precise shutoff and reroutes pumped fluid away from an obstructed outlet to prevent pump damage.